10/28/2002 @ 12:00AM

Sensors gone wild

An experiment in the California desert and an executive suite in Tokyo provide tantalizing hints of how a networked world could make everyday life a lot more precise and profound.

Biologists at the James San Jacinto Mountains Reserve in southern California stumbled upon a tiny discovery in the world of squirrels a few months back. It turns out that the little guys, heretofore known to exist on nuts and berries, have a thing for moss; they munch on it for the moisture. No one knew; no one had been in the right place at the right time to see it.

But the squirrel in California was caught in the act when the animal tripped a 7.5-centimeter-square motion sensor that fired up a tiny wireless camera to record the event. The small sensor is one of dozens of digital spectators linked into a speedy wireless network and sprinkled across a 12-hectare patch of wilderness 40 kilometers southwest of Palm Springs. The devices take note of the movements of animals, plant growth and such factors as time, temperature, air pressure, wind speed and changes in carbon use.

Animal insights, however, aren’t the point of this $40 million experiment. The real goal is to explore the uses of intelligent sensors, a technology whose promise suddenly seems huge. The applications for this “embedded intelligence” are vast and profound. Eventually large swaths of the earth will communicate with the digital realm using millions of miniature sensors. “We will really be able to instrument the physical world,” says Deborah Estrin. She’s a computer science professor at UCLA who runs the Center for Embedded Networked Sensing, which oversees the James Reserve project.

Sensors will be placed in bridges to detect and warn of structural weakness and in water reservoirs to spot hazardous materials. Hospitals will track patients with such things as wireless bandages that warn of infection. Truck drivers will be able to dodge traffic jams based on slow-ups 20 cars ahead. Urban planners will track groundwater patterns and how much carbon dioxide cities are expelling, enabling them to make better land-use decisions.

“I like to be conservative about things, but in a way [sensor networks] could be bigger than the internet. The net is relegated to a small screen and a keyboard. This will detect who you are and where you are. The whole analog world will interface with the net,” says Clark Nguyen, a professor of electrical engineering on leave from theUniversity of Michigan to develop sensors for the U.S. Department of Defense’s Advanced Research Projects Agency (DARPA).

DARPA has made sensors a top priority, putting up $160 million of its own money and $500 million in matching funds from other U.S. government agencies. The Pentagon wants what it calls “hyperspectral” data from a war zone. By spreading thousands of chips from a drone aircraft, the military will be able to follow enemy troops and detect bioweapons and electromagnetic noise.

Early this year a pilotless aircraft sprinkled three dozen cheap wireless magnetic sensors, each about the size of a credit card, along a road at the Marine Corps Air Ground Combat Center in Twenty Nine Palms, California. Once they hit the ground, these sensors automatically formed a wireless network and began to scan the environment for magnetic signals. When a vehicle rolled by, they could tell from its magnetic signature what kind it was, its speed and direction. The readings were sent wirelessly through the aircraft to headquarters.

Before the sensor revolution can truly take off, researchers must overcome some crucial engineering hurdles in power management and data networking. The progress made by such companies as Intel and Transmeta in producing low-power chips has helped make processing bits a much thriftier affair, says Estrin. But efficiencies have not kept pace when it comes to transmitting those same bits of data. The James Reserve still uses expensive, short-lived batteries. Estrin wants chips that sip power so slowly they can run on their own for years.

Some new sensors are getting so small–some are invisible to the naked eye–that they will be able to run on 100 microwatts. (A microwatt is a millionth of a watt. A Pentium 4 processor runs at 75 watts.) At the 100-microwatt level they could gather energy from ambient heat and photovoltaic cells, says Stephen Senturia, a specialist in microsystems at MIT. His colleagues are working on making chips so small that they can power themselves, like watches that need only the kinetic energy generated by movements of the wearer’s wrist.

Engineers also have to devise new networking schemes to juggle the billions of constant inputs that could easily swamp network bandwidth. This is Estrin’s top priority at the James Reserve project. Ethernet and TCP/IP, the internet’s two fundamental protocols for shuttling data around, are poorly suited for low-power wireless sensor networks. The net compensates for its habit of losing or garbling lots of data packets by constantly resending to the same address, leaning heavily on plugged-in servers at the edge of the network, fast Cisco routers and abundant bandwidth in between.

Estrin’s plan, still in a rudimentary stage, calls for far less indirection to conserve communication power. Data packets are processed every step of the way along the network, not just at the edge. They zip around with no specific address, grouping themselves on the fly based on a time stamp, a location or the nature of the data being sent (video, audio, chemical signature). And the network must operate only when necessary. Radios have to turn themselves off when they sit idle. “Even listening uses precious joules,” she says.

One matter of little concern is money, thanks to the deflationary forces of Moore’s Law. Airbag sensor chips cost only 60 cents each; they combine an accelerometer with a microprocessor that figures out whether you have merely slammed on the brakes or had an accident. They detect 15 types of information, including speed, deceleration, yaw, vibration and angle, then use algorithms to figure out what it all means. To detect and process this information using traditional instruments would cost more than a thousand dollars.

Omron, a company in Kyoto, Japan, with $5.8 billion in revenue that dwarfs the startups that dominate the sensor business in the U.S., hopes to get around a Japanese slump in industrial demand for sensors by aggressively developing consumer applications. One product it sells lets your car call you to say that it has been stolen, then use a global-positioning system (GPS) to report its location to a security company (for more on this technology, see story, p. 36).

Omron is about to market a system that lets your car recognize you using your fingerprint. The car will be able to prevent unauthorized people from driving it. Omron also sells sensors that adjust air-conditioning and lights according to what room you’re in and remind you to turn things off when you leave.

Omron’s biggest hopes lie with face-recognition software. At its offices in Tokyo, such software replaces keys and cards in the executive suites. It has rather limitless applications in the next decade.

The hitch: these networks are a snooper’s dream come true, putting each citizen in the same situation as that squirrel in the James Reserve. “There would be a whole suite of sensors in a room that could tell you how many people are there and what they are saying. The implications of this are so huge that we need to get sociologists and legal people thinking about this early,” says Roger T. Howe, the director of the Sensor &Actuator Center at the University of California at Berkeley.